Japan Atomic Energy Agency is developing chemical reactors for a pilot test plant of thermochemical IS process. Sulfuric acid (H2SO4) decomposer, one of the key equipments of IS process plant, can vaporize concentrated sulfuric acid and decompose it into SO₃ and H₂O using sensible heat of high temperature helium gas. Feasibility of a sulfuric acid decomposer featuring multi-block-type heat exchanger made of SiC ceramics was examined by preliminary analysis of structural strength, test-fabrication of the ceramic block, and seal performance tests between SiC blocks and metal flanges. Multi-phase flow analysis code coupled to chemical reaction was developed to establish a system of “design by analysis” for facilitating the development of chemical reactors. The codes handles process solutions which exhibit complicated phase behavior. Performance of the codes was confirmed by preliminary bench model analyses, which reproduced behavior of chemical gas absorption and also of liquid-liquid phase separation phenomena.

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High temperature arc plasma produced by employing Gas Tungsten Arc (GTA) is highly controllable, since it is stabilized with a shielding gas. Additionally, GTA requires low cost for equipment investment. Therefore, it is widely utilized as a heat source for material processing such as melting, cutting and welding, or decomposition and detoxification of toxic waste. Energy source properties of GTA strongly depend on the physical properties of the shielding gas. For instance, helium (He) gas or admixture of He gas with argon gas is employed as the shielding gas for conditions requiring high productivity in GTA welding process. Since He has low electrical conductivity especially in low temperature range due to high ionization potential, the current channel in He arc plasma is constricted near the arc axis. Consequently, the enhanced heat input intensity into a base material by the constriction increases weld depth and, thus, leads to the high productivity. However, the effect of the admixture on the heat input characteristics to the base metal is still not clear. In this paper, energy source properties of Ar-He GTA are predicted. The properties of arc plasma and the heat input intensity into a water-cooled copper anode are numerically analyzed.

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The viscosity of molten SiO₂-CaO-MgO-TiO₂ slag was measured using a rotating cylinder method at the concentration of TiO₂ 0˜20 mass% at 1673 K. At SiO₂:CaO:MgO=60:25:15, 55:30:15 and 50:35:15 (mass% ratio), the viscosity of molten SiO₂-CaO-MgO-TiO₂ slag decreased with increasing the concentration of TiO₂. The experimental results were compared with the calculated results from Urbain′s model which reproduced well the present experimental values in molten SiO₂-CaO-MgO-TiO₂ slag.

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